Re: [PATCH] drivers/base: cacheinfo: validate device node for all the caches

[Mark Rutland <mark.rutland@arm.com>]

On Mon, Feb 16, 2015 at 02:10:16PM +0000, Sudeep Holla wrote:
> On architectures that depend on DT for obtaining cache hierarcy, we need
> to validate the device node for all the cache indices, failing to do so
> might result in wrong information being exposed to the userspace.
> 
> This is quite possible on initial/incomplete versions of the device
> trees. In such cases, it's better to bail out if all the required device
> nodes are not present.
> 
> This patch adds checks for the validation of device node for all the
> caches and doesn't initialise the cacheinfo if there's any error.
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Reported-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/base/cacheinfo.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
> index 6e64563361f0..7015bf05c828 100644
> --- a/drivers/base/cacheinfo.c
> +++ b/drivers/base/cacheinfo.c
> @@ -62,15 +62,21 @@ static int cache_setup_of_node(unsigned int cpu)
>  		return -ENOENT;
>  	}
>  
> -	while (np && index < cache_leaves(cpu)) {
> +	while (index < cache_leaves(cpu)) {
>  		this_leaf = this_cpu_ci->info_list + index;
>  		if (this_leaf->level != 1)
>  			np = of_find_next_cache_node(np);
>  		else
>  			np = of_node_get(np);/* cpu node itself */
> +		if (!np)
> +			break;
>  		this_leaf->of_node = np;
>  		index++;
>  	}
> +
> +	if (index != cache_leaves(cpu)) /* not all OF nodes populated */
> +		return -ENOENT;
> +
>  	return 0;
>  }
>  
> @@ -189,8 +195,10 @@ static int detect_cache_attributes(unsigned int cpu)
>  	 * will be set up here only if they are not populated already
>  	 */
>  	ret = cache_shared_cpu_map_setup(cpu);
> -	if (ret)
> +	if (ret) {
> +		pr_err("failed to setup cache hierarcy from DT\n");

It would probably be better if this were something like:

pr_warn("Unable to detect cache hierarcy from DT for CPU %d\n",
	cpu);

Otherwise, this looks sane to me, and it would be nice to have this in
ASAP so as to avoid exposing erroneous information to userspace. So:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
Mark.

>  		goto free_ci;
> +	}
>  	return 0;
>  
>  free_ci:
> -- 
> 1.9.1
> 
>